Combination core and plug bit



United States Patent 2,708,105 COMBINATION CORE AND PLUG BIT Edward B. Williams, Jr., Greenville, Tex. Application August 31, 1953, Serial No. 377,284 3 Claims. (Cl. 255-72) This invention relates to bits for drilling earth formations and has for its principal object to provide a combination drill and core bit composing a conventional core bit, an adapter for connecting the core bit with a drill pipe, and a plug bit mounted within the adapter for drilling out the core made by the core bit.

Other objects of the invention are to provide the plug bit with a skirt or hood portion conforming to the inner diameter of the core bit whereby the core that is formed enters the plug bit before the plug bit begins to drill out the core; to provide a bit structure arranged to drill off the core in conformity with the cutting action of the core bit so as to avoid chippingolf large particles from the core; to provide for flow of drilling fluid across the cutting face and around the cutting elements of the plug bit while maintaining a portion of the drilling fluid in properly directed flow to the core bit; and to provide the plug bit with a transverse groove of relatively large capacity for discharge about the core in parallel relation with the axis of the core bit so as to adequately supply the core bit with drilling fluid that is substantially free of cuttings produced by the plug bit.

In accomplishing these and other objects of the invention as hereinafter pointed out, I'have provided improved structure the preferred form of which is illustrated in the accompanying drawings wherein:

Fig. 1 is a vertical section taken through a combination bit embodying the features of the present invention.

Fig. 2 is a perspective view of the parts of the combination bit shown in disassembled spaced relation.

Fig. 3 is a view similar to Fig. l but with the section taken at right angles to that of Fig. 1.

Fig. 4 is a cross section through the assembled bit on the line 4--4 of Fig. 3 and looking in the direction of the arrows.

Fig. 5 is a reduced vertical section through the lower portion of a borehole being drilled with a combination bit constructed in accordance with the present invention, a portion of the bit being shown broken away and in section to better illustrate the core formed by the core drilling element of the bit.

Referring more in detail to the drawings:

1 designates a combination bit embodying the features of the present invention and which utilizes as a part thereof, a conventional core bit 2 ordinarily used for making a core of an earth formation when drilling a bore hole, as when prospecting for various minerals. The core bit 2 has a ring like body 3 provided with inner and outer cutting faces 4 and 5 and an end cutting face 6. The cutting faces 4, 5 and 6 are provided with cutting elements 7 which in the illustrated instance are diamonds or the like suitably arranged to cut the outside diameter of a core 8, a bottom 9 and wall 10 of a bore hole 11.

The inner face 4 of the core bit is provided with circumferentially spaced vertically arranged grooves 12 that join with radial grooves 13 extending across the face 6 to connect with vertical grooves 14 in the drilling face 5. The grooves form watercourses for a drilling fluid to cool the bit and wash the cuttings from the drilling faces and carry them to the top of the bore hole 11.

The core bit has a collar 15 provided with internal threads 16 for ordinarily connecting the core bit to a core barrel (not shown) that in turn connects the core bit with a drill pipe 17 by which the bit is rotated and ice through which the drilling fluid is supplied to the bit. Such core bits are eflicient in cutting hard formations and similar, but solid, bits are also used in drilling the bore hole 11 when the core 8 is not required.

It is obvious that bits of this character are very expensive and necessitate considerable investment in the two types of bits that are used in drilling the bore hole. With the present invention, a substantial reduction in investment is made by utilizing a combination bit whereby the full diameter of the bore hole may be drilled utilizing a core bit in connection with a relatively small plug bit 18 and an adapter 19. When a core is desired, the core bit 2 may be removed from the assembly, attached to a core barrel (not shown) and operated in accordance with conventional core drilling practice. p

The adapter 19 has a generally cylindrical body 20 of less diameter than the diameter of the outer cutting face 5 of the core bit to provide an upflow passageway 21 therearound (see Fig. 5) when the combination bit is in use. The upper end of the adapter 19 has an annular bevel 22 terminating in an annular shoulder 22 encircling an externally threaded pin 23 by which the adapter is attached to the drill pipe 17 by which the combination bit is rotated and through which a supply of drilling fluid is supplied to an axial flow passageway 24 within the adapter. The lower end of the adapter 19 has a reduced annular extension 25 provided with external threads 26 for engaging the internal threads 16 on the core bit 2 when the core bit is applied thereto. The reduced extension 25 forms with the body 20 of the adapter, a stop shoulder 27 which abuts against the annular shoulder 22 0f the collar 15. The end face 28 of the extension 25 may engage an internal shoulder 29 of the core bit 2 as shown in Figs. 1 and 2. I

Formed Within the body of the adapter 19 and opening inwardly coaxially of the extension 25 is a cylindrical recess 30 connecting with the flow passageway 24 through an internally threaded recess 31 having threads 32 for attaching the plug bit 18, the internally threaded recess 31 being of smaller diameter than the inner cylindrical face 33 of the recess 30 to provide an internal shoulder 34.

The plug bit 18 includes a cylindrical body 35 having a circumferential face 36 snugly engaging the inner face 33 and which is of a length substantially conforming to the depth of the recess 30. The cylindrical body 35 has a reduced externally threaded pin 37 extending axially therefrom for engagement within the threaded recess 31 in the body of the adapter. The plug also has a stop shoulder 38 for engagement against the shoulder 34. The bottom end of the plug is recessed to provide a generally cylindrical cutting face 39 rounding as at 40 into a generally conical cutting face 41 with the cutting faces provided with alternate ridges 42 and grooves 43 that extend substantially parallel witha plane extending through the axis of the plug and terminating short of opposite diametrical sides of the recess to accommodate angularly arranged grooves and ridges 44 and '45 respectively.

The cutting faces are transversed across the ridges 42 by grooves 46 and 47 that connect with and extend laterally from opposite sides of an axial bore 48 which forms a continuation of the bore 24 of the body of the adapter 19. The bore 48 connects with the lateral grooves through a port 49 that is oflset from the axis of the plug as shown in Figs. 3 and 4 to supply drilling fluid to the lateral grooves 46 and 47. This oifset of the port from the axis of the bit allows the positioning of cutting elements 50 directly in the center of the plug and assures a cutting action across the entire face of the plug.

The ridges are provided with cutting elements 51 that are arranged along the ridges in any suitable pattern but the cutting elements on one ridge are staggered from those of the adjacent ridges so that the cuts are spread in a desired manner. This is best obtained by arranging the grooves in spiral sequence as indicated by the lines 52 in Fig. 4. The successive cut from cutting element to cutting element may be varied by changing the rate of curvature of the spiral.

The grooves 46 and 47 are relatively deeper than the grooves 43 and 44 in the cutting faces of the plug in order to effect the proper division and distribution of the drilling fluid to adequately supply all of the drilling faces, flush the cuttings from around the cutting elements, and remove heat from the drilling faces. It will be noted that the relatively deeper transverse grooves follow the contour of the drilling faces of the plug 1.8 to discharge directly into the space between the exterior face of the core 8 and the inner cutting face 4 of the core bit 2.

Since the inner diameter of the cylindrical portion 39 of the cutting face of the plug bit 18 conforms with the inner diameter of the inner cutting face 4 of the core bit 2, the core enters freely within the plug bit before the cutting elements of the plug begin to drill off the core. This is an important feature because it eliminates chipping otf of large particles from the outside of the core that would interfere with the drilling operation. To facilitate insertion of the plug bit the pin 37 thereof is provided with diametrically opposed grooves 53 and 54 for receiving the lugs of a socket wrench (not shown) and which may have a shank that is extended through the bore 24 to engage the lugs thereon with the grooves 53 and 54 for tightening the pin 37 of the plug bit 18 within the interiorly threaded recess of the adapter.

Assuming that the bore hole is to be fully drilled across the entire diameter thereof, the plug bit 18 is mounted within the adapter 19 and the core bit 2 is screwed on to the adapter. The pin 23 of the adapter is then threaded into the lower tool joint of the drill pipe and lowered into the bore hole as in the usual manner. A drilling fluid is then supplied through the drill pipe and the drill pipe is rotated so that the cutting elements remove portions of the formation.

As the core is produced by the cutting faces of the core bit 2, the core 8 moves into the recess of the plug bit without the sides of the core being chipped off or the core being broken. As soon as cutting elements of the plug engage the top of the core, the core is reduced and the cuttings are washed away by the drilling fluid passing through the grooves of watercourses.

A portion of the drilling fluid passes through the grooves 46 and 47 to supply a substantial portion of the drilling fiuid free of cuttings to the cutting face 4 of the core bit. The flow of drilling fluid is discharged from the grooves 46 and 47 of the plug bit along with the cuttings for discharge around the core through the vcrtical passageways of the inner cutting face of the core bit. The position of the grooves 46 and 47 in the plug bit assures directional flow of the fluid so that the fluid streams enter the core bit in directions parallel with the rotational axis thereof in the same manner and in the same direction as the fluid is passed to the core bit when it is being used on a core barrel.

When it is desired to take a core, the core bit 2 is removed from the adapter 19 and the core bit is applied to the core barrel which in turn is mounted on the drill pipe as in conventional practice. After the desired amount of core has been made, the core is removed along with the string of drill pipe and the core bit.

The core bit 2 is removed from the core barrel and attached to the adapter 19, after which the adapter is reconnected with the drill pipe. The string of drill pipe is again lowered into the bore hole. The drilling operation may then continue to drill out the full diameter of the bore hole.

From the foregoing it is obvious that I have provided a combination bit which is adapted to utilize a conventional core bit in conjunction with a small plug bit for drilling out the full diameter of a bore hole when core drilling is not desired. When core drilling is desired the drilling may proceed by using the same core bit without the adapter and plug bit.

What I claim and desire to secure by Letters Patent is:

1. A combination bit including an adapter having a recess in one end and a threaded pin on the other for connection of the adapter to a drill pipe, 2 core bit having a ring-shaped body provided with an end drilling face and inner and outer upwardly extending annular drilling faces, said core bit having a connection with the adapter, a plug bit in said recess of the adapter and having a threaded pin engaging within an internally threaded extension of said recess, said plug having a depending skirt portion provided with an inner circumferential drilling face substantially conforming in diameter with the inner drilling face of the core bit and forming an upward continuation thereof to receive a core therein made by the core bit when in use, and said plug bit having a transverse cutting face joining with the circumferential drilling face of the skirt portion and adapted for drilling off the core.

2. A combination bit including an adapter having a recess in one end and a threaded pin on the other for connection of the adapter to a drill pipe, a core bit having a ring-shaped body provided with an end drilling face and inner and outer upwardly extending annular drilling faces, and having threaded connection with the adapter, a plug bit in said recess of the adapter and having a threaded pin engaging in an internally threaded portion of said recess, said plug having a depending skirt portion provided with an inner drilling face substantially conforming in diameter with the inner drilling face of the core bit and forming an upward continuation thereof to receive a core therein made by the core bit when in use, and said plug bit having a substantially coni' cal cutting portion joining with the circumferential drilling face of the skirt portion and adapted for drilling off the core.

3. A combination bit including an adapter having rccess in one end and a threaded pin on the other for connection of the adapter to a drill pipe, a core bit having a ring-shaped body provided with an end drilling face and inner and outer upwardly extending annular drilling faces and having removably threaded connection with the adapter, said adapter having a drilling fluid passageway opening into said recess, a plug bit in said reces of the adapter and having a threaded pin engaging within an internally threaded extension of the recess, said plug having a depending skirt portion provided with an inner drilling face substantially conforming in diameter with the inner-circumferental drilling face of the core bit and forming an upward continuation thereof to receive a core therein made by the core bit when in use, and said plug bit having a substantially conical cutting face joining with the circumferential drilling face of the skirt portion and adapted for drilling off the core, said plug bit having an axial water course connected through the pin thereof with the water course of the adapter and terminating in laterally diverging grooves extending across the conical cutting face and downwardly of said skirt portion for supplying drilling fiuid to the drilling faces of the core bit.

References Cited in the file of this patent UNITED STATES PATENTS 2,256,092 Koebel et al. Sept. 16, 1941 2,264,617 Carpenter et al. Dec. 2, 1941 2,381,415 Williams, Jr. Aug. 7, 1945 2,506,341 Bullock May 2, 1950 2,614,809 Zublin Oct. 21, 1952 2,626,780 Ortlotf Ian. 27, 1953 

